Abstract:

Main water source of Haloxylon ammodendron was examined in six different ages (2, 5, 10, 20,and 30 years) of plantations in desert and the ecotone between oasis and desert at southeast edge of Badain Jaran Desert by the stable oxygen isotope technique in autumn (september) 2009. Meanwhile, soil water content was also measured in six different depths (20 cm, 30 cm, 50 cm, 100 cm, 150 cm and 200 cm). The results showed that soil water content in 20-30 cm was significantly higher than 150-200 cm in the all plantations. Soil water in shallow depths was supplied by natural rainfall in late summer and early autumn. With plantation age increased form 2-year-old to 20-year-old, H. ammodendron used more ratio of groundwater and less ratio of shallow layer soil water. Two-year-old H. ammodendron in turn mainly used 100 cm, 20 cm, 30 cm, 50 cm and 200 cm soil water; 5-year-old H. ammodendron in turn mainly used groundwater, 200 cm, 150 cm, 100 cm and 30 cm soil water; 10-year-old H. ammodendron in turn mainly used groundwater, 200 cm, 150 cm, 30 cm and 20 cm soil water; 20-year-old H. ammodendron in turn mainly used groundwater, 200 cm and 150 cm soil water; however, 30-year-old H. ammodendron in turn mainly used 50 cm, 100 cm, 150 cm, 200 cm, 30 cm and 20 cm soil water. At the southeast edge of Badain Jaran Desert, with the increase of plantation age, H. ammodendron had a declined capacity to make use of shallow soil water which is replenished by rainfall, whereas the utilization on deep soil water and ground water was not enough to meet its water requirement of growth. It might be a reason for the large area degradation of H. ammodendron plantations in the region.

Key words: stable oxygen isotope, soil water content, Haloxolon ammodendron plantation